Engineers unveiled the mystery of 500-year-old Leaning tower of Pisa

Why has the Leaning Tower of Pisa survived the strong earthquakes that have hit the region since the middle ages?


The Leaning Tower of Pisa is one of the most remarkable architectural structures from medieval Europe. It is also referred to as the bell tower or campanile. Originally built in the 14th century, the tower has seen many strong earthquakes that have hit the region since the middle ages.

Scientists until now had a puzzle of how this Leaning Tower of Pisa survived the strong earthquakes. This is a long-standing question that a research group of 16 engineers and Professor George Mylonakis, from Bristol‘s Department of Civil engineering and Professor Camillo Nuti at Roma Tre University, now have answered.

Despite leaning precariously at a five-degree angle, leading to an offset at the top of over five meters, the 58-meter tall Tower has managed to survive, undamaged, at least four strong earthquakes that have hit the region since 1280.

In the wake of concentrated accessible seismological, geotechnical, and auxiliary data, the exploration group reasoned that the Tower’s survival could be credited to a phenomenon known as dynamic soil-structure interaction (DSSI).

Scientists found that the softness of the foundation soil makes the structure’s vibrational qualities to be changed significantly, such that the Tower does not resonate with seismic tremor ground movement. This has been the way to its survival. The one of a kind blend of these attributes gives the Tower of Pisa the world record in DSSI impacts.

Professor Mylonakis, Chair in Geotechnics and Soil-Structure Interaction, and Head of Earthquake and Geotechnical Engineering Research Group in the Department of Civil Engineering at the University of Bristol said: “Ironically, the very same soil that caused the leaning instability and brought the Tower to the verge of collapse, can be credited for helping it survive these seismic events.”

Results from the study have been presented to international workshops. They will be formally announced at the 16th European Conference in Earthquake Engineering, taking place in Thessaloniki, Greece, next month [18 to 21 June 2018].

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